This invention relates to the hyperbolic trough-shaped collectors which concentrate the sunlight on a focus and convert it into another energy forms such as heat and electricity.
Currently, trough collectors (solar trough field system) are used to collect the sun's energy in order to obtain electricity and heat therefrom. These systems comprise trough-shaped long parabolic reflectors, thermal receiver tubes which are placed on the focus of the reflectors, and where beams coming from the reflector are collected and in which a fluid exists, and a rotating mechanism which directs the reflectors to the position where the sun is. The beams coming to the reflectors which are directed towards the sun reflect and are collected on the thermal receiver tube which is located on the focus of the reflector. Thermal receiver tube is provided with two nested tubes where a vacuum setting is located in the space therebetween. A fluid, which provides the heat transfer, is passed through the inner tube. The outer tube is made of glass. By concentrating the beams coming from the reflectors on the thermal receiver tube, this tube reaches very high temperatures; therefore, the fluid located in the inner tube can be heated. Heat energy can be converted into the electric energy, when desired, with this fluid which reaches high temperatures. However, the factors such as thermal receiver tubes used in these systems being many meters long, said thermal receiver tubes following the sun together with the reflectors, outer parts thereof being made of glass increase their possibility of breaking during operation. In addition, dynamic and static forces which are generated by the wind can cause both reflectors and tubes to break. In order to decrease the breaking of the parabolic reflectors, a truss structure is formed to support the reflectors on their convex sides. However, this structure decreases only the rate of breaking and is not a complete solution for breaking. The vibrations generated as a result of the movement which is made by the system for directing towards the sun can also cause the glass tubes to break. The solar trough field systems which are built on California (USA) by LUZ can be given as an example for these systems. In that system of LUZ, the parabolic reflectors which are many meters long and the thermal receiver tubes which are located on their focus are rotated together. The most fundamental problem of this system is that the thermal receiver tubes which are made of a fragile material are movable. As long as the thermal receiver tubes are movable, they are subjected to more torque load and the flexible hoses are used in the connections of the beginning and ending points of the parabolic reflectors with the fixed tubes. The thermal receiver tubes which are subjected to the torque loads have a higher possibility of breaking. On the other hand, it is clear that the flexible hose connection is not a safe system since the temperature of the fluid which is transferred within the thermal receiver tube is 300-500° C. In addition, it has been obtained from the field observations that the truss structure, which supports the parabolic mirrors, is also weak against the torque and the moment loads acting due to the drive unit of the system and the wind. Because of these loads, the parabolic reflectors are frequently broken, thus causing the operating costs to increase.
Due to the problems encountered in the above-mentioned system of LUZ, a so-called EUROTROUGH project which is supported by the European Union is initiated. In the scope of this project, the lower part of the parabolic reflectors is supported by a truss structure which can resist more against the torque and the moment loads, and there are inflexible movable tubes attached to the rotary joint on the connection points of the movable thermal receiver tubes with the fixed tubes. Although the truss system which is developed with EUROTROUGH is safer than the system of LUZ, it could not strictly eliminate the breaking problem of the parabolic reflectors and the thermal receiver tubes. It has been understood from the field observations that the possibility of breaking the thermal receiver tubes decreases only to some extent since they are movable in this system as well. In addition, it has been also revealed from the field observations that the hot fluid frequently leaks out from these connections of the thermal receiver tubes comprising rotary joint connection points.
Another problem observed with LUZ and EUROTROUGH is that the hydraulic pistons of both systems cannot move with the required accuracy to follow the sun. It is highly difficult and generates an adjustment problem to make an accurate speed control with the hydraulic piston units and provide simultaneous operations of multiple piston units which are used for multiple parabolic reflectors. Additionally, in both systems, while following the sun, continuous displacement of the center of gravity causes more energy consumption to run these systems.
With the invention, the solar trough field systems with hyperbolic reflector are explained as an alternative to the solar trough field systems with parabolic reflector. In the inventive solar trough field systems with hyperbolic reflector, the sun's energy is used through keeping the reflectors fixed at three different positions in the east, azimuth axis and west directions.
In this invention, the solar troughs with hyperbolic reflector rotating around a fixed thermal receiver tube are used. The hyperbolic reflectors focus the beams coming from a range of 60 degrees from the sun on a thermal receiver tube placed into the focus of a hyperbola, which is located at the bottom point thereof. Therefore, the necessity to direct all hyperbolic reflectors, which are many meters long, with the same accuracy towards the sun is eliminated. Besides, using multiple motor units with lesser capacity instead of a single motor unit which has sufficient capacity to rotate all reflectors in the system, entire system stoppage is prevented even if some of the motors fail. In addition, in order to decrease the maintenance and replacement expenses which will occur in case of breaking the hyperbolic reflectors and more importantly, decrease the manufacturing cost significantly, it is considered to use multi-piece hyperbolic reflectors instead of single-piece parabolic reflectors. Owing to the multi-piece hyperbolic structure, even if some reflector parts are broken, the system can continue to run without suffering too much efficiency loss.
In addition to these, with some changes made on the thermal receiver tube in the collector system as an alternative, the efficiency is ensured to increase. The developments made in this point are related to the use of heat transfer fins within the thermal receiver tubes. On the other hand, an advantage obtained from keeping the thermal receiver tubes fixed is the direct steam generation. Some difficulties are encountered during the direct steam generation in the thermal receiver tubes with flexible hose connection or rotary joint connection which are used in the prior art, and the generated steam leaks out to external environment from said connection points.
An aim of the invention is to form a hyperbolic solar trough field system in which the beams coming from the sun parallel and at angles which change at a fixed rate of 15 degrees per hour throughout the day are concentrated on the focal axis in the bottom part of the hyperbolic reflector that can rotate around this focal axis, and also comprising the thermal receiver tubes which are at a fixed position, extend throughout said focal axis.
Another aim of the invention is to build a hyperbolic solar trough system which is directed towards the sun only by waiting at three positions using the hyperbolic reflectors instead of forming a reflector which is continuously moving. Thus, it is to ensure that the necessity for the movement of the reflector to be fast and accurate at that time is eliminated owing to the beam collection feature of the reflector from a range of 60 degrees.
Also, another aim of the invention is to decrease the maintenance and replacement expenses which will arise in case of breaking the reflectors used as single-piece and to ensure the use of multi-piece hyperbolic reflectors instead of single-piece ones in order to prevent the system from suffering too much efficiency loss even if some reflector parts are broken.
Another aim of the invention is to provide an efficiency increase by using heat fins in the thermal receiver tubes.
Also, another aim of the invention is to ensure that the reflectors are positioned using motors with lesser capacity instead of a single motor unit which has sufficient capacity to rotate all reflectors, and the entire reflector system continues to run even if some of the motors fail.
The hyperbolic solar trough field system is shown in the attached drawings, wherein:
The parts in the figures are numbered one by one and the corresponding terms of these numbers are given below.
Hyperbolic solar trough field system (B)
Hyperbolic solar trough field system (H)
Hyperbolic reflector (20)
Hyperbolic reflector (20m)
Hyperbola form (20m′, 20m″)
Thermal receiver tube (21)
Rotary joint (22)
Side supports (23, 23′)
Pistons (24, 24′)
Azimuth locks (25a, 25a′)
East lock (25d)
West lock (25b)
Guy wires (26, 26′)
Pulleys (27, 27′)
Reflector connections (28)
Support ring (29)
Lightweight Filling Material (30)
The hyperbolic reflector (20) which is contained in said system (B) has a structure which is able to focus the beams coming from a range of approximately 60 degrees from the sun onto the thermal receiver tubes which are located at the bottom part thereof. By means of said system (B), non-imaging type light concentration is generated on the thermal receiver tubes.
Since said hyperbolic reflector (20) is connected to the ground from its bottom part with the rotary joints (22), the reflector (20) can be directed towards the sun by rotating with the use of any drive mechanism which is associated with these joints (22) and/or reflectors (20). Considering that there is a route of movement of approximately 180 degrees between sunrise and sunset, the hyperbolic reflector (20) remains at a fixed position, as in the demonstration in
Since the reflectors (20) in the hyperbolic solar trough field system (B) collect the sunlight from a range of approximately 60 degrees and thus are located only in three positions in a day, the necessity for reflectors (20) to move synchronously with each other during position change is eliminated. Thus, accurate and continuous sun tracking is not needed, and there is no need for the complex electronic control units and programs which are necessary for this tracking. This critical consideration decreases not only the design, manufacturing and maintenance expenses substantially but also simplifies the operation equally.
Besides the sun tracking activity with continuous and accurate movement through the said system (B) decreases the production, maintenance and repair costs of the system (B), the multi-piece reflectors may also be used in order to decrease the costs arising from the single-piece hyperbolic reflector manufacturing.
Another example of the drive mechanisms may be hydraulic or pneumatic pistons (24, 24′) as shown in
In the said hyperbolic solar trough field system (B), the lock mechanisms (25a, 25a′, 25b, 25d) can also be used in order to protect the hyperbolic reflectors (20) from the wind loads and reduce the oscillation amount when they are at a fixed position. Owing to these mechanisms which are positioned on the beginning and ending parts of the hyperbolic reflectors (20), when the reflectors are changed to the fixed position in the east, azimuth axis and west directions, the arms of the lock mechanisms move in the north-south direction and support the reflector (20) in its fixed positions. When the reflectors (20) are changed to the east position, they are kept fixed between the side supports (23′) and the east locks (25d). When the reflectors (20) are changed to the parallel position to the azimuth axis, they are kept fixed between the azimuth locks (25a, 25a′). When the reflectors (20) are changed to the west position, they are kept fixed between the side supports (23) and the west locks (25b).
Different alternatives can be applied for the thermal receiver tubes (21) which are used in the hyperbolic solar trough field system (B). In the first alternative, the thermal receiver tube (21) consists of two tubes which are nested, concentric with each other and have a vacuum space therebetween. A fluid is passed through the inner tube, which is called transfer tube, with high thermal conductivity for the heat transfer. Outer glass tube allows the beams coming from the hyperbolic reflectors to reach directly the transfer tube. The temperature of the transfer tube and the fluid therein increases in this way. In order to avoid heat loss through convection from transfer tube to outside, a vacuum space is created between the glass tube and the transfer tube.
In the second alternative, unlike the previous thermal receiver tube, this tube is made of glass and the heat fins with high thermal conductivity are used therein in order to heat the fluid passing through this tube more quickly. As well as, said heat fins may be the fins which are in the form of a plate; they may be used in the form of pins as well. Plate-shaped fins provide manufacturing and mounting easiness compared to pin-shaped fins. Since the pin-shaped ones cast a less shadow on one another, they are more efficient than the plate-shaped ones. It is possible to use both fin structures in this system (B). In the second alternative, it is required to use a second glass tube on the outer parts of the suitable thermal receiver tubes such that a vacuum space will be between said glass tube and the inner tube. The heat fins which are suitable for the second alternative are located longitudinally inside the glass tube and integrally with this tube.
Since the thermal receiver tube (21) is somewhat surrounded by the hyperbolic reflector (20) in the hyperbolic solar trough field system (B), it is less affected by the external environment conditions. Therefore, since the outer glass tube is not preferred in the thermal receiver tube (21) which is suitable for the above-mentioned first alternative, there is no need to perform the operations such as combining the glass tubes which are many meters long, creating a vacuum space, providing tightness; and there arises an opportunity to save money on the issues such as material, workmanship, maintenance, repair owing to the absence of these glass tubes which are the most fragile components of the system even if they are in a fixed position.
The above preferred hyperbolic solar trough field systems (B) are not intended to limit the protection scope of the invention. According to the information described with the invention, the modifications to be performed on this preferred hyperbolic solar trough field systems (B) should be evaluated within the protection scope of the invention.
The hyperbolic reflector (20m) which is contained in said system (H) has a structure which is able to focus the beams coming from a range of approximately 60 degrees from the sun onto the thermal receiver tubes which are located at the bottom part thereof. With the said system (H), non-imaging type light concentration is generated on the thermal receiver tubes.
Since said hyperbolic reflector (20m) is connected to the ground from its bottom part with the rotary joints (22), the reflector (20m) can be directed towards the sun by rotating with the use of any drive mechanism which is associated with these joints (22) and/or reflectors (20m). Considering that there is a route of movement of approximately 180 degrees between sunrise and sunset, the hyperbolic reflector (20m) remains at a fixed position, as in the demonstration in
In an embodiment of the subject matter of the invention of hyperbolic solar trough field system (H), a support ring (29) was installed on the bottom part of the hyperbolic reflector (20m). Above-mentioned thermal receiver tubes (21) are located on the central axis of the support ring (29). The system (H) rotates around this axis which is also the focal axis of the reflectors (20m). In the hyperbolic solar trough field system (H), the support rings (29) are supported from their bottom parts through rotary joints (22) and rotate on the rotary joints (22) by sliding. The rotary joints (22) were installed below the support rings (29) such that they allow the rings (29) to rotate around their center. In addition, the strength of the system (H) is increased by using a lightweight filling material between the support ring (29) and the hyperbolic reflector (20m).
Since the reflectors (20m) in the hyperbolic solar trough field system (H) collect the sunlight from a range of approximately 60 degrees and thus are located only in three positions in a day, the necessity for reflectors (20m) to move synchronously with each other during position change is eliminated. Thus, accurate and continuous sun tracking is not needed, and there is no need for the complex electronic control units and programs which are necessary for this tracking. This critical consideration decreases not only the design, manufacturing and maintenance expenses substantially but also simplifies the operation equally.
Although the sun tracking activity with continuous and accurate movement through the said system (H) decreases the production, maintenance and repair costs of the system (H), the multi-piece reflectors may also be used in order to decrease the costs arising from the single-piece hyperbolic reflector manufacturing.
Another example of the drive mechanisms may be hydraulic or pneumatic pistons (24, 24′) as shown in
In the hyperbolic solar trough field system (H), the lock mechanisms (25a, 25a′, 25b, 25d) can also be used in order to protect the hyperbolic reflectors (20m) from the wind loads and reduce the oscillation amount when they are at a fixed position. Owing to these mechanisms which are positioned on the beginning and ending parts of the hyperbolic reflectors (20m), when the reflectors are changed to the fixed position in the east, azimuth axis and west directions, the arms of the lock mechanisms move in the north-south direction and support the reflector (20m) in its fixed positions. When the reflectors (20m) are changed to the east position, they are kept fixed between the side supports (23′) and the east locks (25d). When the reflectors (20m) are changed to the parallel position to the azimuth axis, they are kept fixed between the azimuth locks (25a, 25a′). When the reflectors (20m) are changed to the west position, they are kept fixed between the side supports (23) and the west locks (25b).
Different alternatives can be applied for the thermal receiver tubes (21) which are used in hyperbolic solar trough field system (H). In the first alternative, the thermal receiver tube (21) consists of two tubes which are nested, concentric with each other and have a vacuum space therebetween. A fluid is passed through the inner tube, which is called transfer tube, with high thermal conductivity for the heat transfer. Outer glass tube allows the beams coming from the hyperbolic reflectors to reach directly the transfer tube. The temperature of the transfer tube and the fluid therein increases in this way. In order to avoid heat loss through convection from transfer tube to outside, a vacuum space is created between the glass tube and the transfer tube.
In the second alternative, unlike the previous thermal receiver tube, this tube is made of glass and the heat fins with high thermal conductivity are used therein in order to heat the fluid passing through this tube more quickly. Said heat fins may be the fins which are in the form of a plate; however they may be used in the form of pins as well. Plate-shaped fins provide manufacturing and mounting easiness compared to pin-shaped fins. Since the pin-shaped ones cast a less shadow on one another, they are more efficient than the plate-shaped ones. It is possible to use both fin structures in this system (H). In the second alternative, it is required to use a second glass tube on the outer parts of the suitable thermal receiver tubes such that a vacuum space will be between said glass tube and the inner tube. The heat fins which are suitable for the second alternative are located longitudinally inside the glass tube and integrally with this tube.
Since the thermal receiver tube (21) is somewhat surrounded by the hyperbolic reflector (20m) in the hyperbolic solar trough field system (H), it is less affected by the external environment conditions. Therefore, since the outer glass tube is not preferred in the thermal receiver tube (21) which is suitable for the above-mentioned first alternative, there is no need to perform the operations such as combining the glass tubes which are many meters long, creating a vacuum space, providing tightness; and there arises an opportunity to save money on the issues such as material, workmanship, maintenance, repair owing to the absence of these glass tubes which are the most fragile components of the system even if they are in a fixed position.
The above preferred hyperbolic solar trough field systems (H) are not intended to limit the protection scope of the invention. According to the information described with the invention, the modifications to be performed on this preferred hyperbolic solar trough field systems (H) should be evaluated within the protection scope of the invention.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IB06/51421 | 5/5/2006 | WO | 00 | 2/12/2009 |